In Central Park Zoo, Samson the Lion tells his 11-year-old son Ryan stories of his adventures in the wild. That night, when the zoo closes, all the animals are free to roam. Samson, along with his friends Benny, Bridget, Larry, and Nigel compete in a turtle curling championship while Ryan is with his friends. Ryan accidentally causes a stampede which head to the game. Samson and Ryan have a falling-out and Ryan storms off before Samson can apologize. Ryan wanders into a green box and gets shipped away by a truck, which the legend tells will take him to the wild. With the help of a pigeon, Hamir, Samson and Benny go after him, sneaking into a garbage disposal truck with Nigel, Larry, and Bridget coming as well, accidentally throwing Benny off the truck. After passing through Times Square and nearly being crushed in the garbage disposal, the group encounters a pack of rabid stray dogs. Samson leads them through the sewer rather than scaring them off. There, they take directions to the docks from two street wise alligator brothers, Stan and Carmine. The next morning, the four friends steal a tugboat during a hectic escape from New York harbor. With help from Larry, they drive the boat and reunite with Benny, who has enlisted a flock of Canada geese to help lead the crew in the right direction of Ryan’s ship. Days later, Nigel goes mad and, under the impression they have hit an iceberg, jumps overboard.
The boat runs aground in Africa, where the group quickly discover that all the animals in the area are being evacuated by the carriers, as a nearby volcano erupts. They witness Ryan escaping, but he runs into the jungle. Samson attempts to find him, but it is quickly revealed that he has in fact never been in the wild before after trying to eat a rude Hyrax. The rest of the group head back to the ship, but Samson decides to keep trying to find his son. While walking, Samson starts seeing plants and rocks change colors. Nigel is captured by a group of wildebeests who dwell in the volcano, and their leader Kazar, pronounces him ‘The Great Him’, based on an ‘omen’ he received when he was young: about to be devoured by lions, a toy koala fell from the sky (actually from a plane) and scared the lions away, saving his life. Kazar wants to change the food chain; he would rather see “prey become predators” and vice versa. For this, he needs to eat a lion. Bridget and Larry are also captured and held prisoner.